Ulrey's tetra

Geographic Origin and Biotope: Paraguay River basin in South America. Inhabits the lush flooded lagoons of the Pantanal and streams with thick patches of plants and floating water lilies.

Taxonomy and Morphology: Ulrey's Tetra (Hemigrammus ulreyi). Often wrongly labeled and confused with Hyphessobrycon heterorhabdus (Flag tetra). Differs in its stocky profile and the absence of the continuous red line.

Social Behavior: Subtle elegance in a school. Less frantic than an Hasemania, it navigates with measured darts but cannot do without a large group (at least 8 specimens) to move in sync.

Coloration and Sexual Dimorphism: Sober and metallic: semi-transparent body surmounted by a clear triple white-black-yellow horizontal line along the flanks (flag), with a black-spotted dorsal fin bordered with yellow. Slender males; very corpulent females at the waist.

Aquarium Setup: Classic planted tank, shielded lighting and horizontally positioned tree trunks. A carpet of low plants (Eleocharis, Lilaeopsis) gives them a great sense of security.

Diet and Feeding: Microscopic mouths, require freeze-dried crumbs. Micro-predators: they like daphnia, frozen Cyclops and decapsulated lobster eggs, but they regularly pounce on normal basic flakes.

Water Quality: Robust cyprinid that excels at temperatures of around 24-25°C (75-77°F) and forgives beginners in case of small nitrate accumulations, remaining active even if the values are not amateur-pure.

Compatibility and Tankmates: Fantastic as a schooling fish for Loricariids, Apistogrammas (Borellii) and excellent cohabitation with southern pencilfish (Nannostomus). It is totally defenseless against aggression, never mix with Midas Cichlids or similar.

Aquarium Reproduction: Careless egg scatterer in mosses or dense plants in the early morning, with the male ramming the partner's flanks to induce ovarian discharge. They cannibalize the eggs in minutes.

Risks and Diseases: Identity confusion at purchase: make sure you buy true Ulreyi. Sensitive to the classic thermal shocks or fluctuating pH typical of newly set up tanks (new tank syndrome).